Nine-Switch Resonant AC-DC Converter for Low-EMI Power Density
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Solution Overview
Problem
Conventional three-phase AC-DC converters require a large number of semiconductors, leading to reduced power density and efficiency due to hard-switched components, which also generate electromagnetic interference (EMI).
Innovation Solution
A nine-switch front-end converter integrates a boost PFC rectifier and high-frequency resonant converter into a single stage, with six switches soft-switched and three semi-soft-switched, reducing the semiconductor count and increasing switching frequency, while using delta-connected resonant tanks to minimize DC ripple and stress on capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional three-phase AC-DC converters use hard-switched semiconductors, then the converter can operate at lower switching frequencies, but the power density is reduced and EMI is generated
Solution Approach 1:
The patent changes the switching mode from hard-switching to soft-switching by modifying the circuit topology to include resonant tanks and auxiliary circuits that create zero-voltage or zero-current switching conditions. This parameter change in switching methodology reduces both switching losses and EMI generation simultaneously.
Solution Approach 2:
The patent introduces resonant tanks and auxiliary switching circuits as intermediary elements between the main power switches and the load. These intermediaries create soft-switching conditions that reduce switching losses and minimize EMI without requiring direct hard-switching of the main power devices.
2Productivity
If conventional converters use twelve semiconductors with six hard-switched, then the converter structure is simpler, but the switching frequency is limited and power density is reduced
Solution Approach 1:
The patent segments the converter into multiple independent phases (three-phase interleaved configuration), allowing each phase to operate at high switching frequency independently. This segmentation enables the use of fewer semiconductors per phase while achieving higher overall power density and switching frequency.
Solution Approach 2:
The patent employs preliminary action by using auxiliary circuits and resonant tanks to prepare the switching conditions before the main power switches operate. This preliminary preparation creates soft-switching conditions that enable higher frequency operation with reduced semiconductor requirements.
3Power
If the converter uses more semiconductors, then the power density increases, but the device complexity and cost increase
Solution Approach 1:
The patent makes each semiconductor device perform multiple functions: main power switching, resonant switching, and EMI filtering. This multi-functionality allows the converter to achieve high power density with fewer semiconductors by eliminating the need for separate components for each function.
Solution Approach 2:
The patent merges the resonant tank circuits with the main power conversion circuitry, combining multiple functions into integrated structures. This merging reduces the total semiconductor count while maintaining high power density through efficient use of each component.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration results in a more compact, efficient, and cost-effective converter with reduced EMI, enabling higher power density and longer component lifespan by allowing higher switching frequencies and soft-switching operations.
Implementation Method 1
convert electrical power between the DC potential and a set of three tank circuits operated at their respective resonant frequency
Implementation Method 2
a coupling transformer, configured to bidirectionally couple AC electrical power at the switching frequency
Data Source
AI summary
A bidirectional AC power converter, having a front-end comprising parallel sets of three switches in series, which connects multi-phase AC to coupling transformer through a first set of tank circuits, for synchronously bidirectionally converting electrical power between the multi-phase AC and a DC potential, and for converting electrical power between the DC potential to a bipolar electrical signal at a switching frequency, controlled such that two of each parallel set of three switches in series are soft-switched and the other switch is semi-soft switched; the coupling transformer being configured to pass the bipolar electrical power at the switching frequency through a second set of the tank circuits to a synchronous converter, which in turn transfers the electrical power to a secondary system at a frequency different from the switching frequency.